Field of the Invention
This disclosure relates to a coupling device configured to couple a shaft and a rotating member which can be demounted from the shaft.
Description of the Related Art
Image forming apparatuses such as printers, copying machines, facsimile machines of the related art include a sheet conveyance device configured to separate sheets set in a cassette one-by-one by using a roller and feed the separated sheets to an image forming unit. A roller configured to feed sheets needs to be replaced due to abrasion caused by a long-term use or adhesion of paper powder, and hence the roller is configured to be demountable from a roller shaft. A coupling device in which the roller demountably mounted on the roller shaft is coupled so as not to come off the roller shaft at the time of feeding the sheet is required. At the time of replacement of the roller, it is desired that the roller can be demounted from the shaft easily.
In a mechanism configured to transmit a rotational driving force by a gear as well, there is a case where the gear is replaced. In this case as well, a configuration in which the gear is prevented from coming off from the gear (rotating member), and the gear can be demounted from the shaft easily at the time of replacement of the gear is desired. As a locking device for locking the gear so as not to come off, a configuration in which a snap fit claw provided on a gear abuts against a wall surface of a grove provided on the shaft is proposed (Japanese Patent Laid-Open No. 7-206208). In other words, in this coupling device, the snap fit claw abuts against the wall surface of the groove portion on the shaft, so that the gear is prevented from coming off in an axial direction. In a configuration in which the snap fit claw abuts against the groove portion, removal from the shaft at the time of replacement of the rotating member (gear) by an operation of the snap fit claw.
However, in the case where the rotating members such as the gear and the roller do not rotate integrally with the shaft, that is, when the shaft and a rotating body rotate relatively with each other, the snap fit claw abuts against the wall surface of the groove portion on the shaft, and hence may be worn due to a long-term use. In recent years, durability of products is improved, so that the frequency of usage of the mechanism such as the gear and the rollers is significantly increased. Therefore, wear of the snap fit claw may cause a problem of lowering of a locking function of the rotating members such as the gear and the rollers, which may increase rattling between the rotating members and the shafts thereof or cause rotating member to come off the shaft.